IP telephony has been a focus of research and development in the telecommunications industry for years. One reason the technology has been a focus is because of potential advantages such as converging voice and data networks, simplifying equipment and reducing management requirements, thereby reducing capital expenditures and operating expenditures. However, the deployment of certain services such as IP telephony services has been complicated because the protocol lacks some of the features of protocols specifically developed for support of telephony such as Asynchronous Transfer Mode (“ATM”).
One particular feature that is not a fundamental part of the IP protocol is admission control. It is known to employ a static model of IP network capacity in conjunction with calculated over-provisioning and special quality of service techniques such as per-flow bandwidth reservation or class-of-service per-hop queuing-priority behavior to help avoid a situation where so many IP flows are handled by a network that the IP flows suffers delays or packet loss due to congestion. However, network usage and topology are not static, and over-subscription from high volume can result in degraded service quality and even service failure.